Re: [PATCH V4 11/27] ublk: handle UBLK_U_IO_COMMIT_IO_CMDS

Caleb Sander Mateos
2025-11-30T16:40:01Z

On Thu, Nov 20, 2025 at 5:59 PM Ming Lei <ming.lei@redhat.com> wrote:
>
> Handle UBLK_U_IO_COMMIT_IO_CMDS by walking the uring_cmd fixed buffer:
>
> - read each element into one temp buffer in batch style
>
> - parse and apply each element for committing io result
>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> drivers/block/ublk_drv.c | 117 ++++++++++++++++++++++++++++++++--
> include/uapi/linux/ublk_cmd.h | 8 +++
> 2 files changed, 121 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 66c77daae955..ea992366af5b 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -2098,9 +2098,9 @@ static inline int ublk_set_auto_buf_reg(struct ublk_io *io, struct io_uring_cmd
> return 0;
> }
>
> -static int ublk_handle_auto_buf_reg(struct ublk_io *io,
> - struct io_uring_cmd *cmd,
> - u16 *buf_idx)
> +static void __ublk_handle_auto_buf_reg(struct ublk_io *io,
> + struct io_uring_cmd *cmd,
> + u16 *buf_idx)

The name could be a bit more descriptive. How about "ublk_clear_auto_buf_reg()"?

> {
> if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG) {
> io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
> @@ -2118,7 +2118,13 @@ static int ublk_handle_auto_buf_reg(struct ublk_io *io,
> if (io->buf_ctx_handle == io_uring_cmd_ctx_handle(cmd))
> *buf_idx = io->buf.auto_reg.index;
> }
> +}
>
> +static int ublk_handle_auto_buf_reg(struct ublk_io *io,
> + struct io_uring_cmd *cmd,
> + u16 *buf_idx)
> +{
> + __ublk_handle_auto_buf_reg(io, cmd, buf_idx);
> return ublk_set_auto_buf_reg(io, cmd);
> }
>
> @@ -2553,6 +2559,17 @@ static inline __u64 ublk_batch_buf_addr(const struct ublk_batch_io *uc,
> return 0;
> }
>
> +static inline __u64 ublk_batch_zone_lba(const struct ublk_batch_io *uc,
> + const struct ublk_elem_header *elem)
> +{
> + const void *buf = (const void *)elem;

Unnecessary cast

> +
> + if (uc->flags & UBLK_BATCH_F_HAS_ZONE_LBA)
> + return *(__u64 *)(buf + sizeof(*elem) +
> + 8 * !!(uc->flags & UBLK_BATCH_F_HAS_BUF_ADDR));

Cast to a const pointer?

> + return -1;
> +}
> +
> static struct ublk_auto_buf_reg
> ublk_batch_auto_buf_reg(const struct ublk_batch_io *uc,
> const struct ublk_elem_header *elem)
> @@ -2708,6 +2725,98 @@ static int ublk_handle_batch_prep_cmd(const struct ublk_batch_io_data *data)
> return ret;
> }
>
> +static int ublk_batch_commit_io_check(const struct ublk_queue *ubq,
> + struct ublk_io *io,
> + union ublk_io_buf *buf)
> +{
> + struct request *req = io->req;
> +
> + if (!req)
> + return -EINVAL;

This check seems redundant with the UBLK_IO_FLAG_OWNED_BY_SRV check?

> +
> + if (io->flags & UBLK_IO_FLAG_ACTIVE)
> + return -EBUSY;

Aren't UBLK_IO_FLAG_ACTIVE and UBLK_IO_FLAG_OWNED_BY_SRV mutually
exclusive? Then this check is also redundant with the
UBLK_IO_FLAG_OWNED_BY_SRV check.

> +
> + if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
> + return -EINVAL;
> +
> + if (ublk_need_map_io(ubq)) {
> + /*
> + * COMMIT_AND_FETCH_REQ has to provide IO buffer if
> + * NEED GET DATA is not enabled or it is Read IO.
> + */
> + if (!buf->addr && (!ublk_need_get_data(ubq) ||
> + req_op(req) == REQ_OP_READ))
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
> +static int ublk_batch_commit_io(struct ublk_queue *ubq,
> + const struct ublk_batch_io_data *data,
> + const struct ublk_elem_header *elem)
> +{
> + struct ublk_io *io = &ubq->ios[elem->tag];
> + const struct ublk_batch_io *uc = &data->header;
> + u16 buf_idx = UBLK_INVALID_BUF_IDX;
> + union ublk_io_buf buf = { 0 };
> + struct request *req = NULL;
> + bool auto_reg = false;
> + bool compl = false;
> + int ret;
> +
> + if (ublk_dev_support_auto_buf_reg(data->ub)) {
> + buf.auto_reg = ublk_batch_auto_buf_reg(uc, elem);
> + auto_reg = true;
> + } else if (ublk_dev_need_map_io(data->ub))
> + buf.addr = ublk_batch_buf_addr(uc, elem);
> +
> + ublk_io_lock(io);
> + ret = ublk_batch_commit_io_check(ubq, io, &buf);
> + if (!ret) {
> + io->res = elem->result;
> + io->buf = buf;
> + req = ublk_fill_io_cmd(io, data->cmd);
> +
> + if (auto_reg)
> + __ublk_handle_auto_buf_reg(io, data->cmd, &buf_idx);
> + compl = ublk_need_complete_req(data->ub, io);
> + }
> + ublk_io_unlock(io);
> +
> + if (unlikely(ret)) {
> + pr_warn("%s: dev %u queue %u io %u: commit failure %d\n",
> + __func__, data->ub->dev_info.dev_id, ubq->q_id,
> + elem->tag, ret);

This warning can be triggered by userspace. It should probably be
rate-limited or changed to pr_devel().

Best,
Caleb

> + return ret;
> + }
> +
> + /* can't touch 'ublk_io' any more */
> + if (buf_idx != UBLK_INVALID_BUF_IDX)
> + io_buffer_unregister_bvec(data->cmd, buf_idx, data->issue_flags);
> + if (req_op(req) == REQ_OP_ZONE_APPEND)
> + req->__sector = ublk_batch_zone_lba(uc, elem);
> + if (compl)
> + __ublk_complete_rq(req, io, ublk_dev_need_map_io(data->ub));
> + return 0;
> +}
> +
> +static int ublk_handle_batch_commit_cmd(const struct ublk_batch_io_data *data)
> +{
> + const struct ublk_batch_io *uc = &data->header;
> + struct io_uring_cmd *cmd = data->cmd;
> + struct ublk_batch_io_iter iter = {
> + .uaddr = u64_to_user_ptr(READ_ONCE(cmd->sqe->addr)),
> + .total = uc->nr_elem * uc->elem_bytes,
> + .elem_bytes = uc->elem_bytes,
> + };
> + int ret;
> +
> + ret = ublk_walk_cmd_buf(&iter, data, ublk_batch_commit_io);
> +
> + return iter.done == 0 ? ret : iter.done;
> +}
> +
> static int ublk_check_batch_cmd_flags(const struct ublk_batch_io *uc)
> {
> unsigned elem_bytes = sizeof(struct ublk_elem_header);
> @@ -2783,7 +2892,7 @@ static int ublk_ch_batch_io_uring_cmd(struct io_uring_cmd *cmd,
> ret = ublk_check_batch_cmd(&data);
> if (ret)
> goto out;
> - ret = -EOPNOTSUPP;
> + ret = ublk_handle_batch_commit_cmd(&data);
> break;
> default:
> ret = -EOPNOTSUPP;
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index c96c299057c3..295ec8f34173 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -109,6 +109,14 @@
> */
> #define UBLK_U_IO_PREP_IO_CMDS \
> _IOWR('u', 0x25, struct ublk_batch_io)
> +/*
> + * If failure code is returned, nothing in the command buffer is handled.
> + * Otherwise, the returned value means how many bytes in command buffer
> + * are handled actually, then number of handled IOs can be calculated with
> + * `elem_bytes` for each IO. IOs in the remained bytes are not committed,
> + * userspace has to check return value for dealing with partial committing
> + * correctly.
> + */
> #define UBLK_U_IO_COMMIT_IO_CMDS \
> _IOWR('u', 0x26, struct ublk_batch_io)
>
> --
> 2.47.0
>